The review was conducted in the context of the Using Peer Support In Developing Empowering Mental Health Services (UPSIDES) Study, which is a multi-national research study using the Consolidated Framework for Implementation Research [24] to investigate PSW implementation in low-resource setting [25].
Protocol and registration
The protocol of this systematic review was developed in accordance with PRISMA guidelines [26] and registered on PROSPERO (International Prospective Register of Systematic Reviews) on 24 July 2018: CRD42018094838.
Eligibility criteria
Inclusion criteria were: (participants and intervention) studies about PSWs supporting adults 18 aged years or older with a primary diagnosis of mental illness; (outcome) identifies implementation facilitators or barriers for PSW implementation; (study design) randomised controlled trials, controlled before and after studies, cohort studies, case–control studies, cross-sectional studies and qualitative studies. Publications were included if reported in English, French, German, Hebrew, Luganda, Spanish or Swahili (chosen as languages in UPSIDES Study sites), with a date of publication on or before July 2018. Exclusion criteria were: substance misuse or addiction populations; intervention was mutual aid, peer-run organisations, naturally occurring peer support, peer navigation interventions and peer support delivered exclusively online. No studies were excluded on the basis of comparators, control conditions or setting.
Information sources
Six data sources were used: (1) the electronic bibliographic databases (n = 11) searched were MEDLINE (OVID), EMBASE (OVID), Cumulative Index of Nursing and Allied Health Literature (CINAHL) (EBSCHO), PsycINFO (OVID), Scopus, Web of Science, Google Scholar, OpenGrey, ProQuest Dissertations & Theses A&I, African Journals OnLine (AJOL) and Scientific Electronic Library Online (SciELO); (2) table of contents of Psychiatric Services and Psychiatric Rehabilitation Journal (chosen as publishers of PSW studies); (3) conference proceedings of European Network for Mental Health Service Evaluation (ENMESH) (n = 14, 1994–2017) and Refocus on Recovery (n = 4, 2010–2017) (chosen as recovery-relevant academic conferences with available proceedings); (4) websites (peersforprogress.org; cpr.bu.edu) (chosen as they host PSW materials); (5) a preliminary list of included publications was sent to experts (n = 38) requesting additional eligible publications; (6) forward citation tracking on all included records using Scopus and backward citation tracking through a hand-search of reference lists of included publications.
Search strategy
The search strategy was adapted from a published systematic review concerning peer support for people based on statutory mental health services [27]. The search strategy was modified for each database, and an example of the search strategy used for MedLine is shown in Online Resource 1. All searches were conducted from inception until July 2018.
Study selection
After removing duplicates, the titles and abstracts of all identified citations were screened for relevance against the inclusion criteria by DT, with a randomly selected 5% sample independently assessed by RN. Concordance between the two reviewers was 93%. Full texts were single screened by DT. Data extraction was then conducted on 10% of the included publications independently by DT and RN, who discussed their data extraction to check for adequate agreement. Date extraction for the remaining 90% of included publications was then conducted.
Data abstraction
For each included publication, information was extracted on (1) study participant inclusion and exclusion criteria, (2) a summary of the peer support intervention, (3) a summary of the characteristics of the PSW, (4) where the intervention was carried out including country and service setting and (5) factors that influenced implementation, whether the factor enabled or hindered implementation and the evidence that the stated implementation factor influenced implementation.
Quality assessment
The Critical Appraisal Skills Programme (CASP) was used to assess the quality of eligible studies. CASP checklists do not provide an overall scoring, so a scoring system used in a previous systematic review [28] was applied. Each CASP item rated ‘yes’ scored 1 point and each item rated ‘no’ scored 0 points. The percentage score for the 10-item CASP randomised controlled trial checklist, the 10-item CASP qualitative checklist, the 12-item CASP cohort checklist and the 11-item CASP case control checklist was calculated, with studies scoring ≥ 60% graded as good quality, studies scoring 45–59% graded as fair quality and studies scoring below 45% graded as poor [29, 30].
Analysis
A three-stage modified narrative synthesis [31] was conducted on the included papers. In stage 1 (developing a preliminary synthesis), facilitators and barriers to implementation of peer support work identified in included studies were synthesised. Findings were tabulated and an initial coding framework was developed through thematic analysis to group-related facilitators and barriers within overarching themes, called influences. Vote counting of the number of papers identifying each theme was performed to establish the strength of the theme. A preliminary draft of the implementation framework was developed and refined by analysts. In stage 2 (exploring relationships between studies), the implementation influences were compared for studies using a group-based modality (defined as one or more PSWs meeting several service users in a group) versus individual modality (defined as a PSW meeting a service user individually). Stage 3 (assessing the robustness of the synthesis) used two approaches. First, the findings from sub-group analysis of higher quality studies (rated as good) were compared with the framework from all included studies. Second, the identified influences coded in at least 10% of papers were adapted into a measure of PSW implementation readiness. The resulting Implementation Measure, shown in Online Resource 5, comprised eight items, each rated on a four-point scale: 0 (few or no facilitators present, many or all barriers present), 1 (more barriers than facilitators present), 2 (more facilitators than barriers present) or 3 (many or all facilitators present, few or no barriers present). The sum score ranges from 0 (implementation most difficult) to 24. The measure was completed by the site lead in each of the six sites participating in the UPSIDES Study: Ulm (Germany), Hamburg (Germany), Kampala (Uganda), Dar es Salaam (Tanzania), Beer Sheva (Israel) and Pune (India). The sites include low-income (Kampala, Dar es Salaam), lower-middle (Pune) and high-income sites (Ulm, Hamburg, Beer Sheva), and sites with (Hamburg, Kampala, Beer Sheva, Pune) and without (Ulm, Dar es Salaam) experience of implementing peer support work. The goal was to provide preliminary evidence that the synthesis identified influences specific to peer support work (convergent validity) and not to generic influences such as resource level (discriminant validity).